1. Field of the Invention
The present invention relates to a technique of detecting a pointing position, which is pointed with a pointing device having a light emitter, in a display image.
2. Description of the Related Art
A projector that causes images output from a computer to be projected and displayed on a screen is generally used for presentation. A presenter gives explanations while pointing at an arbitrary position in a computer image displayed on the screen with a pointing device.
It is very convenient and desirable that the presentation system detects the pointing position, which is pointed with the pointing device, for a diversity of processing. In the recent trend, the presenter has accordingly used a pointing device having a light emitter, such as a laser pointer. The system has a shooting device that takes photographic images of the presentation aspect. The system causes the photographic image to undergo a predetermined series of processing, so as to detect the pointing position. A concrete procedure of the system binarizes the photographic image with a fixed threshold value and computes a position of a center of gravity in one pixel area having relatively high luminance values (effective pixel area), out of two types of pixel areas in the binarized photographic image (binary image), so as to detect the pointing position.
In some cases, however, the prior art technique has difficulties in accurately detecting the pointing position.
For example, an increase in angle between the normal direction of the screen and the pointing device having the light emitter expands the area irradiated with the light emitter, for example, to a quasi-elliptical shape. In the prior art system, the threshold value is fixed, so that not only the vicinity of the pointing position but its peripheral region are extracted into the binary image as an effective pixel area. This causes the position of the center of gravity in the effective pixel area to be deviated from the pointing position. It is accordingly difficult to accurately detect the pointing position.
The object of the present invention is to solve the problems of the prior art technique and thus to provide a technique that detects a pointing position, which is pointed with a pointing device having a light emitter, in a display image, with a higher accuracy.
At least part of the above and the other related objects is attained by a first apparatus of the present invention, which is a pointing position detection apparatus that detects a pointing position, which is pointed with a pointing device having a light emitter, in a display image. The pointing position detection apparatus includes: a photographic image capture section that captures a photographic image by shooting the display image including a pointing image generated by light emitted from the light emitter of the pointing device; and a detection processing section that detects the pointing position in the display image according to a luminance property of the captured photographic image. The detection processing section has: a threshold value determination section that determines a threshold value, which is used to binarize the photographic image, according to the luminance property of the photographic image; a binarization processing section that binarizes the photographic image using the determined threshold value, so as to generate a binary image; and a gravity center position computation section that computes a position of a center of gravity in one pixel area having relatively high luminance values, out of two types of pixel areas constituting the binary image, so as to detect the pointing position.
In the pointing position detection apparatus, the detection processing section detects the pointing position using the threshold value, which is determined according to the luminance property of the photographic image. This arrangement allows the pointing position, which is pointed with the pointing device having the light emitter, in the display image to be detected with a higher accuracy.
In the specification hereof, the pixel value is referred to as the xe2x80x98luminance valuexe2x80x99. The pixel value may also be referred to as the xe2x80x98density valuexe2x80x99.
In accordance with one preferable embodiment of the pointing position detection apparatus, the threshold value determination section creates a luminance value distribution, which represents a count of pixels at each luminance value, based on the photographic image, and sets the threshold value equal to a luminance value determined by taking into account the luminance value distribution and a preset threshold value determination condition.
The threshold value can readily be determined by using the luminance value distribution created from the photographic image.
In the above pointing position detection apparatus, it is preferable that the threshold value allows extraction of a pixel area in the binary image which is smaller than an area of the pointing image in the photographic image.
The arrangement of determining the threshold value in the above manner allows extraction of only a neighborhood area surrounding the pointing position, which is pointed by the light emitter of the pointing device, into the binary image, thus ensuring accurate detection of the pointing position.
In accordance with another preferable embodiment of the pointing position detection apparatus, the detection processing section further includes a table that stores a plurality of threshold value determination conditions, which are provided respectively for a plurality of available pointing devices. In this embodiment, the threshold value determination section determines the threshold value using a threshold value determination condition selected among the plurality of threshold value determination conditions.
Selection of a desired pointing device results in determining the threshold value suitable for the selected pointing device. This ensures the detection process of the pointing position adequate for the pointing device.
In the above pointing position detection apparatus, it is preferable that the detection processing section repeatedly carries out detection of the pointing position.
This allows the pointing position to be detected continually.
In accordance with another embodiment of the pointing position detection apparatus, the photographic image capture section has a shooting device that takes the photographic image.
In the above embodiment, the pointing device may have the light emitter that emits either a visible light or an invisible light, and the shooting device may sense a light component emitted from the light emitter.
In the pointing position detection apparatus of the above embodiment, it is preferable that the shooting device has a filter that allows transmission of the light component emitted from the light emitter of the pointing device, while cutting off other light components.
This arrangement gives the photographic image including the pointing image generated by the light emitted from the light emitter of the pointing device, thus facilitating the subsequent steps of the detection process.
In the pointing position detection apparatus of the above embodiment, it is preferable that the shooting device has an aperture to adjust brightness of the photographic image.
This arrangement gives the photographic image suitable for the luminance of the light emitted from the light emitter of the pointing device.
In accordance with one preferable application of the above pointing position detection apparatus, the detection processing section further includes a table that stores a plurality of shooting conditions, which are respectively provided for a plurality of available pointing devices. In this application, the position detection section controls the shooting device to adjust the aperture, based on a shooting condition selected among the plurality of shooting conditions.
Selection of the desired pointing device automatically gives the photographic image suitable for the luminance of the light emitted from the light emitter of the pointing device.
A second apparatus of the present invention is a presentation system that includes: a pointing position detection apparatus having any of the above arrangements; and an image display apparatus that causes the display image to be displayed in a display area.
This presentation system includes the pointing position detection apparatus discussed above and accordingly exerts the similar functions and advantages to those of the pointing position detection apparatus discussed above. Namely the pointing position, which is pointed with the pointing device having the light emitter, in the display image can be detected with a higher accuracy.
In accordance with one preferable embodiment of the present invention, the pointing position detection apparatus causes the detected pointing position to be reflected on predetermined data processing.
This arrangement allows execution of a diversity of processing according to the detected pointing position. One exemplified procedure makes the detected pointing position reflected on the image display apparatus and enables a pointer or a cursor to be shown at the pointing position in the display image.
In the above presentation system, the image display apparatus may be a projector that projects the display image from either one of a front side and a rear side of a screen including the display area.
The present invention is also directed to a method of detecting a pointing position, which is pointed with a pointing device having a light emitter, in a display image. The method includes the steps of: (a) capturing a photographic image by shooting the display image including a pointing image generated by light emitted from the light emitter of the pointing device; and (b) detecting the pointing position in the display image according to a luminance property of the captured photographic image. The step (b) has the steps of: (b1) determining a threshold value, which is used to binarize the photographic image, according to the luminance property of the photographic image; (b2) binarizing the photographic image using the determined threshold value, so as to generate a binary image; and (b3) computing a position of a center of gravity in one pixel area having relatively high luminance values, out of two types of pixel areas constituting the binary image, so as to detect the pointing position.
This method exerts the similar functions and advantages to those of the first apparatus of the present invention discussed above. Namely the pointing position, which is pointed with the pointing device having the light emitter, in the display image can be detected with a higher accuracy.
The present invention is further directed to a computer program product that causes a computer to detect a pointing position, which is pointed with a pointing device having a light emitter, in a display image. The computer program product has: a computer readable recording medium; and a computer program recorded in the recording medium. The computer program causes the computer to attain the functions of: capturing a photographic image by shooting the display image including a pointing image generated by light emitted from the light emitter of the pointing device; and detecting the pointing position in the display image according to a luminance property of the captured photographic image. The detection function includes the functions of: determining a threshold value, which is used to binarize the photographic image, according to the luminance property of the photographic image; binarizing the photographic image using the determined threshold value, so as to generate a binary image; and computing a position of a center of gravity in one pixel area having relatively high luminance values, out of two types of pixel areas constituting the binary image, so as to detect the pointing position.
The computer executes the computer program included in this computer program product to exert the similar functions and advantages to those of the first apparatus of the present invention discussed above. Namely the pointing position, which is pointed with the pointing device having the light emitter, in the display image can be detected with a higher accuracy.
The principle of the present invention is actualized by a variety of applications, for example, a method of detecting a pointing position, a pointing position detection apparatus, a presentation system, a computer program that attains the method or the functions of the apparatus, a recording medium in which the computer program is recorded, and a data signal that includes the computer program and is embodied in a carrier wave.